There is known a detection element using an organic conversion layer of organic material as a semiconductor layer that converts a radiation into an electric charge. The detection element detects a radiation by detecting an output signal corresponding to an electron-hole pair generated by a radiation that has entered the organic conversion layer. In such a detection element, known is a configuration in which a thickness of an organic semiconductor layer is increased to improve detection sensitivity for a radiation other than a gamma ray.
However, as the thickness of the organic conversion layer increases, a hole generated in the organic semiconductor layer tends to lose energy before reaching an electrode, and get buried in thermal fluctuation and disappear. It follows that only an electron having high energy reaches the electrode from which an output signal is taken out. As a result, the output signal includes not only dependency on the number of electron-hole pairs but also position dependency related to a generation position of the electron-hole pair in the organic semiconductor layer. Thus, in the related art, detection sensitivity is lowered in some cases.